The present invention is directed to breathable elastomeric films and nonwoven materials and laminates thereof. Such laminates have a wide variety of uses, particularly in the areas of limited use and disposable items.
Films have been traditionally used to provide barrier properties in limited use or disposable items. By limited use or disposable, we mean that the product and/or component is used only a small number of times, or possibly only once, before being discarded. Examples of such products include, but are not limited to, surgical and health care related products such as surgical drapes and gowns, disposable work wear such as coveralls and lab coats, and personal care absorbent products such as diapers, training pants, incontinence garments, sanitary napkins, bandages, wipes and the like. In personal care absorbent products, such as infant diapers and adult incontinence products, films are used as the outer covers so as to prevent body wastes from contaminating the clothing, bedding and other aspects of the surrounding environment of use. In protective apparel, such as hospital gowns, films are used to prevent cross exchange of microorganisms between the wearer and the patient.
Although these films are generally effective barriers with respect to water vapor and the like, they are not aesthetically pleasing because their surfaces are smooth and either feel slick or tacky and they are visually unappealing, making them less desirable in apparel applications and other uses where they are in contact with human skin. Thus, it is desirable that these items be more cloth-like, both from a tactile and visual standpoint. For example, infant diapers that have the feel and appearance of traditional cloth undergarments are perceived as premium products, overcoming the tendency in some cases to believe that they need to be covered by outer garments for aesthetic reasons. In addition, garment-like isolation gowns for use in hospital environments most likely would increase the comfort of the wearer while reducing the apprehensiveness of the patient. It is also preferable to provide an outer cover material with more elastic give and recovery to provide better fit and comfort.
Laminates of films have been used to create materials which are both impervious and somewhat cloth-like in appearance and texture. One example of such a laminate is the outer cover on disposable diapers.
A primary purpose of the film in such laminates is to provide barrier properties. However, there is also a need that such laminates be breathable so that they can transmit water vapor which, in turn, requires that the film be breathable. Apparel made from laminates of breathable or microporous films are more comfortable to wear because they reduce the water vapor concentration and the consequent skin hydration underneath the apparel item.
Accordingly, there is a need for an inexpensive laminate having a soft outer cover and good elastic and breathability properties which provides both cloth-like aesthetics and the fit and comfort desired by the wearer.
This invention is directed to films which do not inherently pass water vapor, but which are rendered porous to water vapor while remaining impermeable to liquid water, and to laminates employing such films. This invention is also directed to films which do inherently pass water vapor, for which the rate at which water vapor passes through is increased, and to laminates employing such films. Certain polymers, such as some polyurethanes, polyether esters, and polyether amides, inherently pass water vapor. The water vapor dissolves in the polymeric film, diffuses through the film, and evaporates from the other side. However, this diffusion process is often too slow, requiring that very thin films or specialty polymers be used to compensate. By loading the polymer with a filler material and stretching the resulting film so as to form micropores in the film in accordance with this invention, water vapor transport therethrough can be increased.